DESCRIPTION OF THE BISBEE QUADRANGLE By Frederick Leslie liansome. INTRODUCTION. Fifty or sixty miles south of the river rise the San the Mexican border past Tucson, Florence, and country. The hills become relatively low, and Francisco Mountains. They are all volcanoes, and four Phoenix, and thence northwestward to Needles, near before Tombstone is reached are divided into semi­ PHYSIOGRAPHIC DIVISIONS OF ARIZONA. of them are of large dimensions. The largest, San Fran­ the California line. The Mountain Region and detached clusters by broad embayments of Quater­ cisco Mountain, nearly 13,000 feet high, might be The Territory of Arizona may be divided into classed among the largest volcanic piles of the West. the Desert Region are both included in the Basin nary alluvium, continuous with that flooring San three physiographic regions (see fig. 1). The first Around these four masses are scattered many cones, and Range system of Gilbert. Pedro or Sulphur Spring valleys. Just southeast of these, occupying the northeastern portion of the the lavas which emanated from them have sheeted over The main drainage of the Mountain and Desert of Tombstone these island-like hills connect the Territory, is included within the Colorado Plateaus, a large area. The foundation upon which they are regions is transverse to the trend of the ranges, main mass of the Mule Mountains with the south­ that wonderful province which the writings of planted is still the same platform of level Carboniferous through the Gila, Salt, and Williams rivers, into ern end of the linear Dragoon Range, and form a strata which stretches calmly and evenly from the base the Colorado River. The minor drainage is by low divide between Sulphur Spring and San Pedro Powell, Gilbert, and Dutton have made classic of the Vermilion Cliffs for more than 150 miles south­ ground in geology. This division, which within ward, patched over here and there with the lingering streams, many of them intermittent in character, valleys. the boundaries of Arizona has an area of about remnants of lower Permian strata and isolated sheets of occupying in general the valleys between the par­ Five miles southeast of Mule Pass the width of 45,000 square miles, drains northward, through basalt. South of the San Francisco Mountains the level allel ranges. the range contracts rather abruptly to about 5 Carboniferous platform extends for 20 or 30 miles, and miles, and this narrowed portion decreases in gen­ the Colorado Chiquito (Little Colorado), Rio LOCATION OF THE BISBEE QUADRANGLE. Puerco, and smaller streams, into the Grand Can­ at last ends abruptly in the Aubrey Cliffs, which face eral altitude toward the Mexican border, where southward and south westward, overlooking the sierra The Bisbee quadrangle is in Cochise County, in the range terminates in a low, broad pass through yon of the Colorado. Its southeastern limit trav­ country of central Arizona. erses the Territory in a general southeasterly the southeastern part of Arizona and within what which the international boundary line runs from direction from the Grand Wash, near the eastern It is the rolling, partly timbered surface of this has been termed the Mountain Region. It lies Sulphur Spring, Valley to the valley of the San border of Nevada, to the New Mexico line, a few great plateau, surmounted by isolated volcanic between the meridians 109° 45' and 110° 00' and Pedro. The geological structure of the southeast­ miles northeast of Clifton. This limit is not every­ mountains, which surrounds the traveler as he the parallels 31° 30' and 31° 20', the latter being ern end of the Mule Mountains continues across where clearly defined. For about 240 miles, extend- journeys across the Territory from New Mexico, locally the Mexican boundary line. The area of this pass, however, and the Morita Hills in Mexico, by way of Holbrook and Flagstaff, to Ash Fork on the quadrangle is about 170 square miles, and just south of the boundary line, are made up of in O2; from the mouth of Diamond Creek on the Colo- rado River to the Adcinity of Fort Apache, the edge the Atchison, Topeka and Santa Fe Railroad. includes the southeastern half of the Mule Moun­ rocks similar to those composing the southern end of the plateau is marked, according to Gilbert in The second physiographic division, which may tains, one of the smaller of the isolated ranges of the Mule Mountains. the Wheeler Survey reports, by the continuous line be called the Mountain Region, adjoins the Plateau characteristic of the Mountain Region of Arizona. On their northeast side the Mule Mountains pre­ of the Aubrey Cliffs, which divide the waters of Region on the southwest, and is essentially a broad The Mule Mountains, while less markedly linear sent a fairly straight front, their slopes rising with zone of short, nearly parallel ranges extending than the Dragoon, Huachuca, Chiricahua, and moderate steepness from the gently inclined detrital diagonally across the Territory from the southeast other neighboring ranges, have a general north­ plain forming the. southwestern part of Sulphur corner northwesterly to Colorado River. The west-southeast trend. They may be considered as Spring Valley. The line separating the mountains width of this zone may be taken as from 70 to 150 extending from the old mining town of Tombstone from the San Pedro Valley on the southwest is miles, but, as will be later seen, its southwestern to the Mexican border, a distance of about 30 much more sinuous and the mountain front is boundary is not susceptible of precise demarcation. miles. On the northeast they are separated by the more variable in slope and height. Gently sloping It is characterized by numerous nearly parallel, broad, flat floor of Sulphur Spring Valley from plains continuous with the floor of the main valley short ranges, separated by valleys deeply filled with the Chiricahua Range, and on the southwest by extend, bay-like, into the mountain mass. The fluviatile and lacustrine deposits. The individual the similar broad valley of .the Rio San Pedro town of Naco lies in such an embayment, which in ranges, such as the Dragoon, Chiricahua, Pinalino, from the Huachuca Range. this case not only extends into the Mule Moun­ Caliuro, Santa Catalina, Tortilla, Final, Supersti­ The town of Bisbee, with an estimated popula­ tains, as Espinal Plain, but separates this range tion, Ancha, and Mazatzal mountains, rarely tion of about 6000, is crowded into a few narrow, from the San Jose Mountains in Mexico, just exceed 50 miles in length or 8000 feet in altitude. confluent ravines near the heart of the range, 7^ southwest of Naco. Their general trend is nearly northwest and south­ miles north of the international boundary. On Within the Mule Mountains may be distinguished east, but near the Mexican border it becomes the east it is connected by the El Paso and South­ two topographic divisions, based upon geological more nearly north and south, and the mountain western Railroad with the new town of Douglas, structure and roughly separated by a northwest- zone as a whole coalesces with a belt of north-south in Sulphur Spring Valley, and with Deming and southeast . line passing through Bisbee, through ranges which extends northward through New El Paso; on the west, branches of the same road run Mule Pass, and down Tombstone Canyon. North­ Mexico and borders the Plateau Region on the to Naco, on the Mexican boundary, and to Benson, east of this line the mountains are sculptured from east. The northwesterly belt of Arizona is on the main line of the Southern Pacific Railroad. comparatively soft Mesozoic beds striking approxi­ described by Gilbert as continuous with the Basin At Douglas connection is made with the Nacosari mately with the trend of the range and dipping at FIG. 1. Map showing physiographic regions of Arizona. Range system of Nevada and Utah, and is consid­ Railroad to Cos, and at Naco with the Cananea, generally moderate angles toward Sulphur Spring ered by him as exhibiting the same prevailing type Yaqui River and Pacific Railroad to Cananea, thus Valley. The slopes of these hills are comparatively the Colorado Chiquito from those of the Gila. of orographic structure. He states that his exam­ bringing the new smelting town of Douglas within smooth, although the occurrence of a hard fossil- These cliffs are well shown at the southwestern inations "have demonstrated no anticlinal struc­ reach of the important mines at Nacosari and iferous limestone in the middle of the generally^ are­ edge of the Mogollon Mesa, where tliey form an tures, except as minor features.' ' The usual Cananea in the State of Sonora. naceous group has occasioned a conspicuous and abrupt scarp from 1000 to 2000 feet in height, structure is monoclinal, demonstrably due to fault­ persistent cliff of erosion. TOPOGEAPHY. overlooking the Tonto basin and facing the ing in the Chiricahua and Final ranges, and pre­ Southwest of the divisional line Paleozoic and Mazatzal and Ancha ranges. From Fort Apache sumably so in all the others." With this con­ MULE MOUNTAINS. older rocks prevail. These are generally more eastward to the New Mexico line the plateau clusion the observations embodied in the present As the boundaries of the Bisbee quadrangle resistant to erosion and more heterogeneous in boundary is less distinct. Vast accumulations of folio accord. have been determined without regard to physio­ character than the Mesozoic beds, and have a far volcanic rock have obscured the plateau surface As far as can be gathered from existing descrip­ graphic or geological unity, it is desirable that a more complicated structure. Their erosion has and erosion has partly destroyed its continuity. tions the greater number of the ranges consist brief general account of the topography of the Mule consequently produced a more rugged and less The San Francisco, Mogollon, Blanca (White), and mainly of Paleozoic sandstones or quartzites and Mountains should precede the' more detailed regular topography.